Aromatizing, preserving and colour-forming substances are introduced into meat to be pickled. These aromatizing and colour-forming substances are generally NaCl (salt) or different mixtures of dilute aqueous solutions of nitrite salt mixtures (e.g. sodium ascorbate). The salt solutions thus prepared having different compositions are called "pickling solutions". By applying well-chosen pickling solutions, well-tasting, good-coloured and non-perishable meat products can be obtained.
For introducing the pickling solution into the meat tissue, pickling instruments are applied. The requirement for pickling instruments is that the pickling solution should be introduced into the meat tissue uniformly, under mild conditions (without destruction of the muscle fibres), well distributed and in the possible shortest time.
According to the traditional way of pickling, the meat to be pickled is placed into an open pickling bath and so much pickling solution is poured on it that the meat is fully covered. The pickling solution diffuses this way into the meat tissue in several days. In the case of products with skin, this time can even exceed a month. Though, in this procedure, the penetration of pickling solution is mild, due to its long duration the procedure is not economic enough, thus it is not suitable for industrial application. Another drawback of this procedure is that it may cause local oversalting and surface sintering.
In a newer procedure (see article "Metalquimia" in Hus, 1944, 1, p. 27) pickling solution is injected into the meat by an instrument provided with several parallelly arranged injection syringe. With this procedure, a relatively uniform and quick pickling can be performed, but the pickling solution leaks out for about an additional hour from the openings caused by injection, and the pricks are seen in the meat.
There are procedures and instruments known in which mechanical force is applied on the meat to be pickled, the pickling solution is thus introduced. In such instruments the meat pieces thrown on each other are rotated in the same time when adding the pickling solution, and as a result of this mechanical effect, the surface of meat pieces is loosened, gets spongy, and it absorbs the pickling solution on the surface. In this way, pickling needs a time of about 10-14 hours, which period is divided into operation and rest time. A drawback of this procedure is that it destructs the meat tissue and cannot be carried out in a continuous mode of operation.
In patent WO92/19011 PCT is this method developed further in that that the mechanical effect of rotation is complemented by ultrasound vibration originating from a tubular ultrasound source introduced into a closed tank. The frequency of the ultrasound used is 22-29 kc/s, its power is 0-400 W. The closed tank is exposed alternately to vacuum and a gas containing CO.sub.2. In the meantime, the closed tank is cooled by a cooling jacket. The energy requirement of this method is high, and it is very complicated, thus very costly. It requires complementary instruments such as a vacuum pump, air compressor, cooling water pump and their appliances. The complicated instrument requires much place, it is immobile, and it is not applicable in satisfying smaller gastronomic demands.
In an earlier invention of the inventors of the present invention is described in Hungarian patent 212372. The quick pickling instrument consists of an open tank with a tray immersing into it, and the whole system is fitted on a self-supporting carcass. On the outer bottom side of the tank ultrasound sources are fixed. These ultrasound transducers are operated by a generator of 34-39 kc/s frequency. The operating parts of the instrument are cooled by a ventilator. Bigger or smaller meat pieces are immersed into the pickling solution by placing them on the tray in the open tank, then they are treated continuously with the ultrasound energy of 34-39 kc/s. This way, significantly shorter times of pickling can be achieved as compared to the traditional method. However, a further shortening of pickling times is required in producing pickled meat and other products of desired substance.